A Membrane Peculiar to the Egg in the Gametophyte of Pteridium aquilinum

Abstract

INVESTIGATIONS of the ultrastructure of the cells taking part in oogenesis in Pteridium aquilinum have shown that the mature egg possesses a membrane lying between the plasmalemma and the cellulose wall, and not present in adjacent cells (Fig. 1). After fixation in potassium permanganate and staining with uranyl acetate this additional membrane is electron dense, and it probably therefore consists of lipid or lipo-protein. The membrane is absent from the young egg and the cells preceding it, and there is evidence, which will be presented in detail elsewhere, that the material of which it is composed is derived from organelles which have degenerated during the maturation of the egg.